I emailed Sigma today after seeing the new lenses listed on the DP Review site...disheartening....

My email:

Dear Sir or Ma’am:

I have noticed, increasingly, that all of the new lenses (esp good long glass) being released are for Sigma, Canon and Nikon. Given the popularity of the Pentax cameras as of late, does Sigma intend to start producing K-mount lenses any time soon? I own the 50-500 and the 17-70. I would love more but they’re hard to come by.

Thanks for making sure this email gets to the appropriate decisions makers.

Response:

As of yet I do not have any release dates or production dates for that mount.

They release the others first because they feel there is more of a demand and a bigger market for them.

It is intersting the he uses the adjective "they" to describe the factory.

As a side note, I was looking at a 17-70 f2.8-4.5 DC Macro on the Sigma site just now and the HSM hypersonic motor version was listed as Nikon and the non-HSM is listed as:
SIGMA,
CANON,
NIKON,
SONY/MINOLTA,
PENTAX
In other words, their usual companies that they support. I think when they make a new version of a product, they simply have to start somewhere. Some years ago when I was using Minolta for my 35mm, I noticed the same thing for that brand too. Sigma, Nikon Canon first, depending on resources and demand, and then us guys.